6.9 IDI Strange Hardstarting issues.

[david85]

Funnily enough, I'm actually chasing this same problem right now (Air leak confirmed in my case too). At first it was only a hard cold-start problem, but eventually resulted in a stall after hot restart, when sitting for more than 2 hours. I already found one return line Tee that had a badly dried out O-ring on it. Found some used ones from an old set of injectors that were still *OK*, but I'll probably have to get a new set of new O-Rings.

 

[Cubey]

I have an apparent air intrusion issue but only when parked overnight facing uphill, even with 3/4 tank of fuel, so it’s probably not in-tank.

I shouldn’t have any olives anymore because a previous owner replaced the steel lines after the lift pump with rubber. Parked level? It’s fine. Return lines should be fine, done 6-8 months ago.

Unless there are olives on the steel lines from the IP to injectors?

I just have to avoid parking like that basically.

 

[Ciulster]

I am pretty sure my system has all of the olives. When I changed the IP they were in all of the steel lines and seemed fairly new and soft so I left them in there. The only one I am missing is the small o ring on the IP inlet which I made up for with a buttload of teflon tape. The tape squished up just like an olive would have and it hasn't leaked since. I am currently under the hood working on injector o rings and they seem to be the culprit. They are so shrunken and brittle I can spin them and move them up and down in their groove with no effort. Gotta love Fall in Canada! Fingers crossed this works!

 

[chris142]

Teflon tape wont work. It will seal the threads but not where the line goes through the nut. I used fuel hose cut to length for olives as a temporary repair.

 

[Thewespaul]

As I said before and Chris repeated, Teflon will not work there. It’s good you are replacing the o rings and if they are that bad then that should help your cause, but I would fix that hardline the right way too.

 

[Ciulster]

So o-rings have been changed and the truck fires up fairly well and runs like normal again. Fingers crossed it keeps enough prime to start without giving me too much grief tomorrow! I will probably get around to changing the inlet o-ring next but there are some things that I have never really been clear on.

Is it normal for the 90 degree elbow on the injection pump inlet to turn past where it lines up with the hardline? Or does it rely solely on the o-ring to seal the inlet? Because when I was putting the IP in the truck I noticed when the elbow was screwed in all the way tight it was facing almost the exact opposite direction of where it meets the hard line.

I unscrewed it just enough to get it to connect to the hardline properly, but it just puked fuel. Hence why I taped it to get it to stop leaking. Is it okay to just leave the elbow loose like that to angle properly with the hardline if I have the proper o-ring in place to stop it from leaking? Or does the elbow really need to be screwed in all the way plus the o-ring? Because if it is supposed to screw in fully something must be wrong because I don't see any way of being able to get the hard fuel line to screw back into it.

Until I can figure out where everything goes normally and how everything is supposed to work together properly with that setup I am just going to leave it alone as the truck runs good enough as is. I would like to change over to a proper o-ring, but if the problem is something weird like the threads on the IP are not aligned properly or something I would rather not take my fuel system apart unless I know I can get it back together properly.

 

[david85]

The only one I am missing is the small o ring on the IP inlet which I made up for with a buttload of teflon tape.

Maybe I'm not following, but the only elbow I know of is on the top of the injection pump...which is the outlet, not the inlet. All the IDI's I saw have a hard line connecting the filter head to the rear of the injection pump. There is an elbow at the filter head end, but the bottom end is bent to aim directly into the fuel inlet of the IP.

The upper end in the photo is the filter side, and the lower end feeds into the IP. No need for an elbow down there.

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[Ciulster]

Strange. My system is not like that at all. It has the elbow at the filter head which the hard line screws into like all IDIs. The hard line goes fairly straight down save for a few curves and has an identical connector as the one that mounts up to the filter head elbow. Excuse the duct tape on the throttle cable bracket to keep it from accidentally popping out. Safety third!

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I then have another elbow that screws into the opening on the rear of the IP.

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Notice how the elbow is in at a nice 45 degrees? If I screwed it all the way tight without the use of Teflon it ends up facing downwards to the engine valley slightly towards the driver's side. Teflon tightened it up perfectly and it stopped turning at the perfect spot for the hard line to mount. Teflon tape was applied to the threads on the brass elbow that screw into the silver injection pump body. A line like you showed would not screw into mine as they would both be female ends. The hard line has good olives in it on both the filter elbow side and the IP elbow side.

Am I perhaps missing some sort of straight adapter that screws into the pump and the o-ring sits on that while the hard line screws onto it? Is this is not the stock setup for a very early '83 6.9? Come to think of it a lot of designs on this truck are very different from every other 6.9 I've ever seen which usually happen to be 84 and up. I've probably only seen about 2 other people with 83's and they were late year models that had the 21.5:1 compression ratio instead of the 20.3:1 like mine has.

 

[Thewespaul]

Yep the early engines I’ve seen use a hardline at a top instead of the barbed 90* fitting, so yours is stock.

 

[david85]

Interesting, I don't think I ever had to take that other style of fitting out, so I'm not sure if it normally has an O-ring or not. Is it starting up properly for you now?

As for the duck tape, hehe, mine never stayed put either and it only got worse after the turbo was added. I opted for a pair of zip-ties.

 

[Ciulster]

The truck still seems to be getting a little bit of air in the lines overnight but seems to start up WAY easier now. If I crank with no glowplugs for 8 seconds to prime any air out of the way and then glow for another 8 seconds it fires up almost instantly. Albeit with a little bit of a misfire and white smoke for a few seconds.

The air seems to be just a tiny bit in the filter housing and not so much a huge bubble in the IP and return system anymore, but at least it is driveable now. The only other places I could see air getting in is the schrader valve or perhaps the 90º fitting on the injection pump inlet.

So at least we have narrowed down the elbow is stock. But that still doesn't answer my questions from before. Do I still need the IP inlet o-ring for this barbed fitting or will teflon suffice for this early design? And if I use an o-ring is it okay to leave it unscrewed a bit to match up with the hard line, or is it really supposed to screw in all the way and there is something wrong with my pump?

I mean worst case Ontario I just get an o-ring for it and use teflon tape again to get it to seal the threads in the right spot again. Double the sealing power of the next leading brand!!!! Lol.

 

[bbjordan]

That elbow at the back of the IP does not look stock. It kinda does, but it looks like it has been modified. Below is what mine looks like. This is a pic of a 7.3, but that is what my 6.9 line looks like. No elbow.

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[david85]

But that still doesn't answer my questions from before. Do I still need the IP inlet o-ring for this barbed fitting or will teflon suffice for this early design? And if I use an o-ring is it okay to leave it unscrewed a bit to match up with the hard line, or is it really supposed to screw in all the way and there is something wrong with my pump?.

I see no harm in trying. You're only backing it out by half a turn, so it might still seal but without seeing it in my hand, I can't be 100% sure. I have to replace the O-rings on my injectors pretty soon so I'll have a look at mine to see what it has for an inlet seal.

 

[Ciulster]

How does the elbow-less design even screw into the IP? is there some other piece that screws into the threads of the IP and then the hard line nut screws onto that kind of like the injector lines mount on the IP? Or is the hard line a male end that sticks into the IP and then screws down on something? I just don't see how a line like that would be able to screw into my injection pump without some sort of adapter or something.